To ask someone the time in Spanish, you say:
¿Qué hora es? - What time is it?

To tell the time in Spanish is a little more complicated. For midnight or noon, you begin with es.
es el mediodía - it's noon
es la medianoche - it's midnight

For any time that begins with one o'clock, you begin with es. Let's look at some examples:
es la una menos cuarto - it's fifteen til one
es la una menos veinte - it's twenety til one
es la una - it's one o’clock
es la una en punto - it's one o’clock sharp
es la una y cuarto - it's one fifteen
es la una y veinte - it's one twenty
es la una y media - it's one thirty

For other times, you begin with son.

son las dos - it's two o’clock
son las cinco - it's five o’clock
son las cinco en punto - it's five o’clock sharp
son las cinco y cuarto - it's five fifteen
son las seis menos cuarto - it's fifteen til six
son las tres menos cinco - it's five til three
son las tres y veinticinco - it's three twentyfive
son las cinco menos ocho - it's eight til five
son las ocho y veintidós - it's eight twenty-two
son las cinco y media - it's five thirty

To be more precise, you may express if you are referring to the early morning, morning, afternoon or evening.
son las dos de la madrugada
it's two o’clock in the early morning
son las siete de la mañana
it's seven o’clock in the morning
son las cinco de la tarde
it's five o’clock in the afternoon
son las ocho y media de la noche
it's eight thrity in the evening